I did make this mistake. Guess what the Output window was trying to tell me all the time?

I will not post the whole output log. But here is what it was screaming at me.

1>C:\Program Files\MSBuild\12.0\bin\Microsoft.Common.CurrentVersion.targets(1697,5): warning MSB3274: The primary reference “StarkIndustries.Driver.IMissileSeeker” could not be resolved because it was built against the “.NETFramework,Version=v4.5.1” framework. This is a higher version than the currently targeted framework “.NETFramework,Version=v4.5”.

Yup. The referenced library was targeting .Net 4.5.1 while the project I was including it in was targeting .Net 4.5.

Lesson
Output window can be a live/timesaver. RESPECT ITS AUTHORITAH!!!